In my opinion the Empire look needs to go. In such fantastical realms, having this historical look is doing a disservice to the setting. Some features could be retained, like Warrior Priests, Knightly Orders, Greatswords and Halberds, but with a new look fitting of the High Fantasy setting. Instead of having a renaicansse look, go for breastplates stormcast inspired and chainmail skirts with leather boots . Freeguild generals riding wingless armored griffins, Arquebus loaded with magic crystals with the essence of Azyr, basically Lightning guns, with ammo being infused by Mages, Badass armored warrior priests calling upon the thunder of azyr and blasting chaos left and right Thor style with greathammers.
Make all the weapons and armour with azyr iconography, comets, thunders and griffins.
Bring the High fantasy to the humans, and make them a proper faction worthy of Age of Sigmar.
Especially the armies of Azyr, being around Stormcast for so long, should have developed as a professional army, trying to emulate their champions somewhat.